/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.jena.sparql.engine.iterator;

import org.apache.jena.sparql.algebra.Table ;
import org.apache.jena.sparql.algebra.TableFactory ;
import org.apache.jena.sparql.engine.ExecutionContext ;
import org.apache.jena.sparql.engine.QueryIterator ;
import org.apache.jena.sparql.engine.binding.Binding ;

/**
 * Binary operation done by looping on the left, and materializing the right - this
 * is not streamed on the right See also QueryIterRepeatApply
 */
public abstract class QueryIter2LoopOnLeft extends QueryIter2
{
    protected Table tableRight ;
    private Binding slot = null ;

    public QueryIter2LoopOnLeft(QueryIterator left, QueryIterator right, ExecutionContext qCxt) {
        super(left, right, qCxt);

        // Materialized right.
        tableRight = TableFactory.create(getRight());
        getRight().close();
    }

    @Override
    protected final void closeSubIterator() {
        getLeft().close();
        tableRight.close(); }

    @Override
    protected void requestSubCancel() {
        getLeft().cancel();
    }

    @Override
    protected final boolean hasNextBinding() {
        if ( slot != null )
            return true;
        while (getLeft().hasNext()) {
            Binding bindingLeft = getLeft().nextBinding();
            slot = getNextSlot(bindingLeft);
            if ( slot != null )
                return true;
        }
        getLeft().close();
        return false;
    }

    protected abstract Binding getNextSlot(Binding bindingLeft);

    @Override
    protected final Binding moveToNextBinding() {
        if ( !hasNextBinding() )
            return null;
        Binding x = slot;
        slot = null;
        return x;
    }
}
